A Brief History of Mechanical
Calculators

Part III
Getting Ready for the 20th Century

In 1885, Dorr
Eugene Felt (1862-1930), of Chicago, used a wooden macaroni box,
staples, rubber bands, wire, string, and meat skewers to make a prototype of what became
the first practical multiple order calculator to use a keyboard, the Comptometer.
The "Macaroni Box" prototype is now on display at
the Smithsonian Institution in Washington.

The design was based on a
fast carry mechanism that acted while the keys returned to their original state after
being depressed. A detent toothed lever controlled the wheel momentum by bringing the
wheel to a full stop.

By 1886 Felt had completed his first metal prototype. In
March 1887 he applied for a patent which was granted in October 11, 1887 (US Patent
371,496). Then he started the Felt
& Tarrant Mfg. Co. in partnership with Robert Tarrant.

In 1889, Dorr E. Felt obtained a patent for his
Comptograph which was basically a Comptometer
with a printing device. This machine is now in the Smithsonian Museum. In 1890 Felt also
produced a model with wide carriage able to print several columns of numbers.

In 1957 the Felt & Tarrant Mfg. Co. became the
Comptometer Corporation and had manufacturing operations in the United States and
England. The English operation along with the rights to use the name Comptometer
were sold in 1960 to Control Systems Limited, owner of the Bell Punch Company
Ltd. andits distributor Sumlock Ltd. which became Sumlock
Comptometer Ltd. The US manufacturing operations were stopped and Comptometers
were manufactured in England by using a plastic-metal mechanism of inferior quality [14].
In 1961, the Comptometer Corporation merged with Victor Adding Machine
Co. to form the Victor Comptometer Corporation [8]. The new models
introduced by Victor used the internal Bell-Punch mechanism.

The Comptometer used a "multiple order keyboard" also
called full keyboard which consisted of a matrix with 9 rows of keys, one for
each digit (1 to 9). The number was entered by pressing one digit in each column. There
were no Zero keys because zero was represented by the absence of a keystroke in the
corresponding column. This arrangement of keys, initially introduced by Thomas Hill in
1857, became very popular during the first half of the 20th Century.

In the Comptometer, pressing a key advanced a wheel
mechanism to cause the positional value of that key to be added immediately to the
displayed total. Therefore, for a given position in a number, the user could enter the
non-zero digit or a combination of digits that would add-up to the digit, for example: 3
and 4 instead of 7. Users were also able to press keys simultaneously in several
columns while entering a number. Notice that a full keyboard arrangement already
contains the positional value information for a given digit, which no longer exist with
modern 10-key arrangements where digits must be entered in sequential order. All
these features allowed for faster data-entry tricks used by skilled Comptometer operators.
Subtraction required the addition of the nines complement. A lever on the right side
was used to clear the display. Comptometer operation became a formal profession and
required a lot of training. A good Comptometer operator was able
not only to perform additions and subtractions at fast speed, but also multiplications and
divisions by applying repeated additions and complementary subtractions, respectively.

The usage of the low value digits became so popular that
some companies introduced half-keyboard versions of
the Comptometer. Torpedo (1935), Plus(1935),
and Contex (1950) are
typical examples. These keyboards only had digits from 1 to 5.

Comptometers weighed from 17 to 25 pounds and were priced
between $300 and $400.

William Seward Burroughs

William Seward Burroughs (1857-1898)
worked between 1880 and 1884 in developing an adding machine with a full keyboard and
printing capabilities. He applied for a patent on January 10, 1885, almost two years
before Felt applied for his patent, and was granted the patent on August 21, 1888,
about a year after Felt was issued his patent.

The initial implementation of the printing device printed
the totals but not the individual entries. This limitation was corrected before the patent
was granted.

Once the number was entered in the keyboard, a printing
mechanism was activated when the user pulled a handle on the side of the machine. The
adding wheels were activated when the lever returned to its original position.

In 1886, Burroughs founded the American
Arithmometer Company in St. Louis, Missouri. By 1889 the company had sold about 50
machines, but they were difficult to operate. Burroughs immediately improved them by
inventing the dash pot, a mechanism used to regulate the pull in the
machines handle. He wanted to get a fully reliable and solid adding machine that
would be useful for handling the financial operations in a business. In order to achieve
this objective, Burroughs had to combine his invention with several functional features of
Felts inventions. This is reflected on the patent awarded to Burroughs in May 5,
1892. Burroughs achieved his objective but he only saw the beginning of his success for he
died in 1898.

In 1904 the company moved to Detroit, and in 1905 it was
renamed to Burroughs Adding Machine Co. Twenty years later they had sold about
one million machines and had become the largest manufacturer of adding machines in the
United States. It remained as one of the leading manufacturers of mechanical office equipment until the
1950's. After WW2 it expanded its operations to include computers, and in 1953 its name
was changed to Burroughs Corporation. Finally, in 1986 it merged with Sperry
Corporation to form Unisys Corporation. [9]

Early Burroughs adding machines, like the Class 1 introduced in 1905,
weighed more than 63 pounds and had glass side walls to display its mechanism. Because of
this they were often called fish tanks [10]. They had "blind" printing
mechanisms, meaning that the user was not able to see the printed numbers hidden behind
the machine. A display on the frontal bottom of the machine showed the number entered or
the total. Class 2, introduced in 1910, had two registers and a "transfer
total" key. These models were made until 1914. Burroughs adding machines were
probably the first to use direct addition of negative numbers without complementary subtraction.

William H. Pike Jr. invented the "visible"
printing mechanism while working for Burroughs. This mechanism was used in the Class 3
models, commonly referred to as flatbeds. Pike left Burroughs temporarily
and manufactured his own machines.

Class 3 models with mobile wide carriage were
manufactured between 1911 and 1929. It is a classical example of the elegant design
combined with speed, reliability and durability, typical of Burroughs products. The
machines became very complex, some Class 3 models weighed about 50 pounds and had
more than 5000 parts. Some operations required the movement of about 2000 parts at the
same time! [11]

Burroughs also produced a direct adding machine, the Class 5model, with no printing
capabilities. It was so similar to the Comptometer that Burroughs was sued for it.

The beginnings of the 10-key machine

William W. Hopkins of St. Louis, invented the Standard in
1901. This machine manufactured by the Standard Adding Machine Co., had one row
of 10 digit keys and marked a significant departure from the popular full keyboard.

The following year, in 1902, James I. Dalton
introduced the Dalton,
an adding/printing machine designed by Hubert Hopkins, which
had two rows of five digits with the sequence: [2 4 5 7 9] [1 3 0 6 8]. The Dalton was
very successful and over 150 models were introduced until 1928. Earlier models had glass
walls in the sides showing the internal mechanism.

Other examples of efforts made towards the development of
machines with simplified key arrangements are the Adix(1903), Diera (1906) and Kuli
(1909) adders manufactured by the Adix Company of Pallweber and
Bordt of Mannheim. These machines had only 9 digit keys, the 10th key actually represented the number ten rather than the
digit zero. The reason was that they were used to add single rows of
digits, so the zero had no usage. The
user had to keep track of the higher order digits on the results and reset
the machine before re-entering those digits. The system was not easy to
use and didn't provide significant savings of time, so their production was
shortly discontinued.

In Germany, an interesting case is the Astra
produced by Astrawerke in 1922. It was based on the Dalton machine but had [00,
000] multi-zero keys. Another example based in the Dalton keyboard is the Madix produced in the 1950's by the VEB
Feinwerktechnik Dresden, the former Ascota Werke.'

However, the modern 10-key design arranged in three rows with the sequence: [7,
8, 9] [4, 5, 6] [1, 2, 3] plus a zero key, was introduced in 1914 by Oscar J. Sundstrand
of Rockford, Illinois. Later, with his brother David, he founded the Sundstrand Adding
Machine Co.

The Remington-Rand
is an example of a company that used the new 10-key design by 1920.

In 1927, Sundstrand sold the rights to Underwood-Elliot
Fisher Co. and worked for this company until 1949. In 1950 he joined the Victor Adding
Machine Co.

Christel Hamann

In 1902, Christel Hamann of Berlin, patented the Gauss,
a circular calculator based on a modified Leibniz cylinder actuating on numeral gears
located in a radial direction around the shaft. This was probably the basis for the design
of the Curta calculators in 1943.

In 1905, Hamann
designed for the Mercedes Bureaumaschinenwerke, the Euklid model. This
machine, patented by Hamann in 1911, discontinued the Mercedes-Plus model, and
was sold as the Mercedes-Euklid.

The Euklid was based on a principle different from the
machines made at that time. The machine had a set of ten parallel racks, one for each
digit 0 to 9. Each rack moved a distance proportional to its corresponding digit while
actuating over unidirectional wheels to perform addition, subtraction, multiplication or
automatic division. The Mercedes-Euklid 1 had only stop-division and the racks
were set by levers, but later models, like the Mercedes-Euklid 3 and the Mercedes-Kopernikus
(a very rare model) had automatic division and full keyboard. A rotating crank was used
for multiplication and division.

In 1925, Hamann designed the Hamann-Manus machine,
which has the same exterior appearance as the Odhner machines, but, instead of being based
on the Baldwin/Odhner pinwheel, uses a completely different mechanism. This machine was
produced by the Deutsche Telephonwerke und Kabelindustrie Aktiengesellschaft in
Berlin. There were many models based on the Hamann-Manus mechanism.

The Victor Adding Machine Co.

This company is one of the few manufacturers of mechanical
calculators that survived the technological changes of the electronic revolution. Founded in 1918 by Carl Buehler of Chicago, its
first product was the Victor 110, a full keyboard adding machine similar to the
Comptometer with no printing capabilities designed by Oliver David Johantgen (1875-1932).
Three years later this model was improved to have printing capabilities. It produced
several models such as the series 300 introduced in 1923, the series 500 in 1931, the
series 600 and 700 in 1939. [11]

By 1952 Victor had sold more than one million machines. As noted
before, Oscar Sundstrand joined the company in 1950 and designed the Victor printing
calculator introduced in 1954. Later, in 1961, Victor merged with the Comptometer division
of Felt & Tarrant Mfg. Co. to become the Victor Comptometer Corp.

In 1968 Victor joined forces with Nixdorf and entered into
the market of electronic desktop calculators with the Victor series 1500, and has stayed
strong in this segment of the market until now.

Marchant Calculators

In 1911 Marchant
Calculating Machine Co., of Oakland, started making calculators based on the Original
Odhner calculators. Their first two models were the Pony and the Standard.
Later, in 1923 Marchant adapted a full keyboard to the Pony model, and in the 1940's
abandoned the Odhner pin-wheel to use its own system based on a proportional wheel.
Examples are the model SCM,
and the Figurematic
considered to be one of the fastest calculators of their time.

The Walther Company

Carl Walther, of
East Germany founded the Walther Company in circa 1886. Its main
products were fire arms for hunting and target practice. In 1924, as a way to recover from
the problems caused by Germany's economical depression, the Walther Company started
manufacturing calculators based on the Odhner pin-wheel.

In 1931 it introduced the TASMA line, which included a full
keyboard and had printing capabilities. The company practically dissapeared during the
WW2, but re-emerged after the war in 1948 with a new line of products. The Comtess
(S32) adding machine, the Multa-32 and the Multa-33 calculators
became very popular in Erurope due to its sturdy construction a high reliability.

During the 70's the company started manufacturing
electronic calculators, but it couldn't survive the competition and was closed sometime at
the beginning of the 80's.

Friden

Carl
Friden (1891-1945), a Swedish immigrant to the United States, founded Friden, Inc.
in 1934, and introduced the Friden S, a full keyboard motor-driven calculator based on the
Thomas machine. Early models included the ST and STW.

In 1952, Friden introduced the model SRW with square root function.
It weighed 42 pounds and had both, a full and a 10-key keyboard. The model SRQ introduced
in 1958 had also X² function.

Friden calculators did not have printing capabilities but
were regarded as high quality calculators.

The company was bought by Singer in 1965 after the
introduction of the Friden EC-132, one of the first electronic calculators.

The Curta, a Mechanical Wonder

It was designed by Curt
Herzstark (1902-1988) of Austria, while prisoner at Buchenwald concentration camp in 1943.
The Curta is a cylindrical four function calculator, similar to the Gauss
calculator designed by Hamann in 1905, with a clockwise "operating handle" on
top and sliding digit levers on the side. Digits are displayed in small openings on top of
each lever. Its coffee grinder appearance gives one more meaning to the expression
"number crunching." Paradoxically, Leibnizs stepped drum, which had the
disadvantage of being too bulky, was used, with some clever modifications, as the heart of
this small piece of ingenuity.

Curt Herzstark was not new to the art; his father Samuel Herzstark
(1867-1937), founded in 1905 the Rechenmaschinenwerk Austria Herzstark & Co.
a manufacturer of Thomas based Arithmometers (Austria
models). In 1927, Curt Herzstark also invented a mechanical memory for the Multimator,
a multicolumn machine manufactured by Astrawerke in Germany.

After the war, in 1946, Curt Herzstark was invited by the
Prince of Liechtenstein to establish a manufacturing plant for the Curta in the
Principality of Liechtenstein, east of Switzerland. The company Contina AG was
founded for this purpose and Herzstark entered as partner and technical director. By 1949,
the Curta I, one of the most
impressive displays of high precision craftsmanship among mechanical calculators, was
introduced. In 1950 Curt Herzstark was issued US Patent 2,525,352.

Curt Herzstark sold the patent rights to Contina and
retired in 1952. Contina introduced the Curta
II in 1954. Later, in 1966, Contina was sold to Hilti, a Swiss company.
Hilti continued the production of the Curta until 1972 when the electronic pocket
calculators took over the market.

Bruce Flamm estimates that about
80,000 of the Curta I, and 60,000 of the Curta II were made.

The First Mechanical Binary Computer

In
1936, Konrad Zuse
(1910-1995) a civil engineer from Germany built up in the living room of
his parent’s house in Berlin, the Z1,
the first mechanical binary computer.Zuse had made a thorough analysis of the mechanical calculators
available at that time looking for an efficient way to perform the lengthy
and tiresome calculations required to design building structures.His conclusion was that the decimal approach was not the most
suitable for this purpose and between 1934 and 1936 he designed a binary
device able to store intermediate results in memory and perform sequences
of arithmetic operations programmed in a punched paper tape (old movie
film.) In other words, he invented the binary computer.

Nowadays
when we think of computer memory we associate the concept with memory
chips, in the 60’s the same concept was associated with ferrite core
boards, but in 1936 the concept didn’t exist.It is hard to believe that computer memory could be made up from
metal plates, and that is exactly among many other new concepts what
Konrad Zuse’s genial mind conceived in those days.

Zuse’s
mechanical memory device consisted of 64 words of 22 bits each, arranged
in three storage blocks, one for the sign and exponent, and two for the
mantissa. Each bit was represented by the position of a fixed rod inserted
trough a sliding metal sheet able to move to the right or the left
defining a 0 or a 1.

The Z1 was just the starting point of a series of
impressive developments made by Zuse in the area of digital computers,
including the invention of the first programming language, the Plankalkül.

Electromechanical Calculators

According to George Chase [1], the first motor-driven calculating
machine was the Autarith. This machine was designed by Alexander Rechnitzer, of
Czechoslovakia, in 1902 and manufactured by the Autarith Company, Ltd. Of Vienna.
Based on the Thomas machine, this was also the first calculator to use the automatic
multiplication and division mechanism patented by Rechnitzer.

In 1907, Samuel Herzstark, father of the Curta inventor,
also produced motor-driven versions of his Thomas based calculators in Vienna.

In 1912, the Eclair,
an Odhner type machine introduced in France, was operated by an electrical motor.

In 1913, the Mercedes Bureaumaschinenwerke
introduced the Mercedes-Euklid 7, which was a motor-driven version of the Mercedes-Euklid
1.

In 1915, Marchant provided his Pony model with an
electric motor drive.

In 1920, Leonardo Torres Quevedo
(1852-1936), of Madrid, presented an electromechanical machine wired to a typewriter at
the Paris Calculating Machine Exhibition. It performed the four operations and used the
typewriter as input/output device. A number of typewriters could be supported
simultaneously. The machine was never produced commercially. Torres Quevedo was a very
prolific inventor, he also developed in 1895 his Algebraic
Machine, an analog machine able to calculate the roots of an arbitrary trinomial equation, and an automated mechanical chess!

In 1922, Monroe introduced the electric version of its Model Knon-printing calculating machine. It had a
large external driving motor.

By 1925 Burroughs had most of its models, including Class 1
and 2, available with motor driven options. Motors had evolved from a continuous operation
engaged through a clutch when the addition was performed (1906), to a point where, due to
its high starting power, they ran only while an operation was actually performed.

In 1929, the Walther Company
introduced the EMKD, an electrified version of its Odhner based machines.

In 1931, Victor introduced the Victor 511S-12, its
first electric adding machine.

Friden, a manufacturer of quality electromechanical
calculators is founded in 1934.

By the
1940s electric motor driven mechanical calculators had become a common desktop
fixture in business and engineering offices.

Once those tiny electrons started taking over the guts of
the mechanical calculators, it took little time until they became part of its brain. In
1961, Sumlock Comptometer, of England, introduced the ANITA (A New
Inspiration To Arithmetic), the first electronic calculator, and marked the beginning
of the end of an era that lasted for 338 years.